Embodiments of the invention relate generally to piezoelectric actuators and, more particularly, to a driver circuit for piezoelectric actuators.
Piezoelectric materials are known to change dimensions upon application of an electric field. This phenomenon allows the use of piezoelectric materials to be used as actuators in micro-electro-mechanical system (MEMS) devices. For example, such actuators have been used in synthetic jet actuators that generate a synthetic jet of fluid to influence the flow of that fluid over a surface. A typical synthetic jet actuator comprises a housing defining an internal chamber. An orifice is present in a wall of the housing. The actuator further includes a mechanism in or about the housing for periodically changing the volume within the internal chamber so that a series of fluid vortices are generated and projected in an external environment out from the orifice of the housing. Examples of volume changing mechanisms may include, for example, a piston positioned in the jet housing to move fluid in and out of the orifice during reciprocation of the piston or a flexible diaphragm as a wall of the housing. The flexible diaphragm is typically actuated by a piezoelectric actuator or other appropriate means.
Typically, piezoelectric actuators often require voltages in the tens of volts or higher for proper operation, and some classes of actuators require AC voltages of possibly variable frequency and amplitude. In applications where piezoelectric actuators are interfaced with low voltage circuitry such as in portable, consumer, aviation, or transportation electronic devices, it can be difficult to drive these actuators. For example, when trying to drive a piezoelectric actuator with an AC voltage waveform or one with variable value with peak voltages higher than are available from a power source, known methods often accomplish this goal using complex, inefficient, large, and/or expensive drivers. In addition, many applications where piezoelectric actuators are used call for using minimum power consumption, and inefficient piezoelectric actuator drivers having low efficiencies often fail such minimum power consumption requirements.
Accordingly, there is a need for a system for driving a piezoelectric load so as to provide a highly efficient driver circuit that can operate from a low voltage source and efficiently generate a controllable high voltage AC waveform of variable frequency and amplitude.